Formed in place fixation system with thermal acceleration

ABSTRACT

A subcutaneously formed in place orthopedic fixation device is provided, such as for fixation of the spine or other bone or bones. The device comprises an inflatable member, such as a tubular balloon. A heat source is provided in thermal communication with the interior of the balloon. The balloon is positioned at a treatment site while in a flexible, low crossing profile configuration. The balloon is thereafter inflated with a hardenable media, and heated to accelerate hardening of the media. Methods and delivery structures are also disclosed.

This is a continuation-in-part of U.S. patent application Ser. No.09/976,459, filed on Oct. 10, 2001, which is a continuation-in-part ofU.S. patent application Ser. No. 09/943,636, filed on Aug. 29, 2001,which is a continuation-in-part of U.S. patent application Ser. No.09/747,066, filed on Dec. 21, 2000, which claims priority to U.S.Provisional Patent Application 60/213,385, filed Jun. 23, 2000, entitled“Percutaneous Interbody Fusion Device,” the contents of each of whichare incorporated in their entirety into this disclosure by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to medical devices and, more particularly,to systems for forming orthopedic fixation or stabilization implants inplace within the body, such as by infusing a formable media into acavity. In one application, the present invention relates to minimallyinvasive procedures and devices for forming a spinal stabilization rodin situ.

2. Description of the Related Art

The human vertebrae and associated connective elements are subject to avariety of diseases and conditions which cause pain and disability.Among these diseases and conditions are spondylosis, spondylolisthesis,vertebral instability, spinal stenosis and degenerated, herniated, ordegenerated and herniated intervertebral discs. Additionally, thevertebrae and associated connective elements are subject to injuries,including fractures and torn ligaments and surgical manipulations,including laminectomies.

The pain and disability related to these diseases, conditions, injuriesand manipulations often result from the displacement of all or part of avertebra from the remainder of the vertebral column. A variety ofmethods have been developed to restore the displaced vertebrae orportions of displaced vertebrae to their normal position and to fix themwithin the vertebral column. For example, open reduction with screwfixation is one currently used method. The surgical procedure ofattaching two or more parts of a bone with pins, screws, rods and platesrequires an incision into the tissue surrounding the bone and thedrilling of one or more holes through the bone parts to be joined. Dueto the significant variation in bone size, configuration, and loadrequirements, a wide variety of bone fixation devices have beendeveloped in the prior art. In general, the current standard of carerelies upon a variety of metal wires, screws, rods, plates and clamps tostabilize the bone fragments during the healing or fusing process. Thesemethods, however, are associated with a variety of disadvantages, suchas morbidity, high costs, lengthy in-patient hospital stays and the painassociated with open procedures.

Therefore, devices and methods are needed for repositioning and fixingdisplaced vertebrae or portions of displaced vertebrae which cause lesspain and potential complications. Preferably, the devices areimplantable through a minimally invasive procedure.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the presentinvention, an in situ formable orthopedic fixation rod. The rodcomprises an elongate tubular body, having an interior chamber therein.The body is inflatable from a first, insertion profile to a second,enlarged profile by introducing a curable media into the chamber. Anaccelerator, for accelerating the curing of the curable media is alsoprovided.

In one embodiment, the accelerator comprises a heat source. The heatsource may comprise a resistance heating element, a conductive coil, aplurality of carbon fibers, or other heat sources known in the art. Aheat sensor may additionally be carried by the chamber.

Preferably, the heat source is capable of heating at least a portion ofthe media to at least about 43° C. For some applications, the heatsource is capable of heating at least a portion of the media to at leastabout 60° C.

In accordance with another aspect of the present invention, there isprovided an orthopedic fixation device. The fixation device comprises anelongate flexible tubular body, having a distal end and a proximal end,and a central lumen extending therethrough. A manifold is provided atthe proximal end of the body, comprising at least one port. Aninflatable member having a proximal end, a distal end and an interior isremovably attached to the distal end of the tubular body. A heat sourceis provided in thermal communication with the interior of the inflatablemember. A valve, for resisting the escape of inflation media, isprovided on the inflatable member. The heat source may comprise aresistive heating element, a circulating loop for circulating heatedmedia, an RF antenna, an ultrasound transducer, a microwave antenna or awaveguide.

In accordance with another aspect of the present invention, there isprovided a method of stabilizing an orthopedic fracture or joint betweenadjacent bones. The method comprises inserting at least two anchorshaving ports, into one or more bones. An orthopedic device is deliveredto a position extending between the two ports. The orthopedic device isinflated with a hardenable media, and the media is heated above bodytemperature to accelerate hardening.

In accordance with another aspect of the present invention, there isprovided a method of forming an orthopedic fixation device at atreatment site within the body of a patient. The method comprises thesteps of positioning an outer wall at the treatment site within thepatient, the outer wall defining a chamber therein. A hardenable mediais introduced into the chamber, and the hardenable media is heated toaccelerate hardening, to form the orthopedic device. In one application,the positioning step comprises positioning the outer wall between twobone anchors. The bone anchors may be positioned in adjacent fragmentsof a bone, separated by a bone fracture. Alternatively, the bone anchorsmay be positioned in vertebral bodies of the spine, such that the outerwall spans across an intervertebral disc or disc space. The treatmentsite may also be the interior of a bone, such as in the cancellous bonespace of a long bone such as the femur.

In accordance with a further aspect of the present invention, there isprovided a deployment catheter for deploying an implantable orthopedicdevice. The catheter comprises an elongate flexible tubular body, havinga proximal end and a distal end. An inflatable device is removablycarried by the distal end. An energy source is connected to the proximalend, and a heating element is provided in thermal communication with theinflatable device.

Further features and advantages of the present invention will becomeapparent to those of skill in the art in view of the detaileddescription of preferred embodiments which follows, when consideredtogether with the attached claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a delivery catheter having aninflatable fixation device thereon.

FIG. 2 is a cross-sectional view taken along the line 2-2 of thedelivery catheter of FIG. 1.

FIG. 3 is a side elevational cross section of a proximal portion of thedelivery catheter of FIG. 1.

FIG. 4A is a side elevational cross section of a distal portion of thedelivery catheter of FIG. 1.

FIG. 4B is a detailed view of the inflatable fixation device of FIG. 4A.

FIG. 4C schematically illustrates a cross-section through a compositeformable rod in accordance with one aspect of the present invention.

FIG. 5 is a side elevational view of the inflatable fixation device ofFIG. 1.

FIG. 6 is a cross-sectional view through the inflatable fixation deviceof FIG. 5, in the expanded position.

FIG. 7A is a schematic cross-sectional view of a valve of the inflatablefixation device of FIG. 6.

FIG. 7B is a schematic cross-sectional view of an alternate valve.

FIG. 7C is an end view of the valve of FIG. 7B.

FIG. 8 is a perspective view of the manifold of the delivery catheter ofFIG. 1.

FIG. 9 is a side elevational view of a portion of the spine, having aformable orthopedic fixation system implanted therein.

FIG. 10 is a side elevational view of a bone anchor.

FIG. 11 is a side elevational view of the bone anchor of FIG. 10,rotated 90° about its longitudinal axis.

FIG. 12 is a longitudinal cross-sectional view of the bone anchor ofFIG. 11.

FIG. 13 is a side elevational view of an alternative embodiment of abone anchor, with bone ingrowth apertures.

FIG. 14 is a side elevational view of a screwdriver.

FIG. 15 is a side elevational view of an alternative embodiment of ascrewdriver.

FIG. 16 is a side elevational view of a guidewire directing device.

FIG. 17 is a top plan view of a directing sheath.

FIGS. 18-28 are partial cross-sectional midline sagittal views of aportion of a vertebral column showing an implantation method of thepresent invention.

FIG. 29 is a posterior elevational view of a portion of a vertebralcolumn post-procedure, with two fixation devices mounted thereon.

FIGS. 30-32 are posterior elevational views of a portion of a vertebralcolumn showing a method of the present invention using a directingsheath.

FIG. 33 is a side elevational view of a cross tie held in position by across tie deployment system, in-between a first and a second pediclescrew.

FIG. 34 is a side elevational view as in FIG. 33, illustrating aninflatable connection rod inflated between the first and second pediclescrews, with a cross tie mounted thereon.

FIG. 35 is a posterior elevational view of a portion of a vertebralcolumn, post procedure, with two inflatable connection rods and onecrossbar mounted thereon.

FIG. 36 is a perspective, schematic view of various components of thecross tie system.

FIG. 37 is a perspective view of a cross tie.

FIG. 38 is a side elevational view of a portion of a spine, having analternate crossbar connected to an inflatable connection rod.

FIG. 39 is a posterior elevational view of a portion of a vertebralcolumn, showing the crossbar of FIG. 38.

FIG. 40 is a side elevational perspective view of a tubular crossbarsheath.

FIG. 41 is a side elevational schematic view of the crossbar sheath ofFIG. 40, mounted on a deployment catheter.

FIG. 42 is a schematic perspective view of the crossbar deploymentsystem of FIG. 41, positioned within two pairs of opposing pediclescrews.

FIG. 43 is a partial cutaway side elevational view of a sheath as inFIG. 40, having an inflatable balloon positioned therein.

FIG. 44 is a schematic side elevational view of the distal end ofdeployment catheter having a heated implant removably positionedthereon.

FIG. 45 is a schematic side elevational view of an implant having analternate heating element.

FIG. 46 is a frontal view of the control panel for the heating element.

FIG. 47 is a block diagram of a driver circuit for driving a heatingelement in accordance with the present invention.

FIG. 48A is a side elevational view of an alternate implant inaccordance with the present invention, having a resistance heating coilpositioned therein.

FIG. 48B is an enlarged fragmentary view of the proximal end of theimplant illustrated in FIG. 48A.

FIG. 48C is an end view taken along the line 48C-48C of FIG. 48B.

FIG. 49 is a side elevational schematic view of the distal end of adeployment catheter in accordance with the present invention, with theimplant removed.

FIG. 50 is a side elevational schematic view of the proximal end of thedeployment catheter illustrated in FIG. 49.

FIG. 51 is a side elevational view of the removable junction between thedistal end of the deployment catheter and the proximal end of theimplant.

FIG. 52 is a side elevational view of a stiffening wire in accordancewith one aspect of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the application of the present invention will be disclosedprimarily in connection with a spinal fixation procedure, the methodsand devices disclosed herein are intended for use in any of a widevariety of medical applications where formation of an attachment,bulking, support, fixation or other element in situ may be desirable.

One advantage of the in situ prosthesis formation in accordance with thepresent invention is the ability to obtain access to a treatment sitethrough a minimally invasive access pathway, while enabling theformation of a relatively larger implant at the treatment site. Thisallows procedure morbidity to be minimized, since open surgical cutdownsor other invasive access procedures may be avoided. In addition, the insitu formation in accordance with the present invention allows theformation of an implant having any of a wide variety of customized orpredetermined shapes, due to the ability of the infusible hardenablemedia to assume the shape of the cavity or flexible container into whichit is infused.

The methods and devices of the present invention additionally enableaccess to a treatment site within the body along a curved and eventortuous pathway, through which a preformed prosthesis would not fit orwould not be navigable. The detachable inflatable prosthesis of thepresent invention, removably coupled to the distal end of an elongateflexible tubular catheter body, can be dimensioned for percutaneous,surgical or transluminal advancement and deployment of an inflatable orotherwise curable in place prosthesis in any of a wide variety oforthopedic applications, such as the spine as disclosed in greaterdetail below, as well as long bones, short bones, and associatedligaments and tendons. In addition, the deployment catheter andprosthesis can be dimensioned for transluminal navigation throughout thecardiovascular system, the gastrointestinal tract, the biliary tract,the genitourinary tract, or the respiratory tract (e.g. thetracheobronchial tree). The device may thus be advanced throughartificial access pathways as well as naturally occurring lumens andhollow organs. Additional applications of the in situ device formationtechnology of the present invention will become apparent to those ofskill in the art in view of the disclosure herein.

In connection with spinal fixation applications, the present inventioninvolves inserting one or two or more bone anchors having a connectorsuch as a portal into at least a first and a second adjacent ornonadjacent vertebra. An implantable, inflatable orthopedic device isinserted through the portals and inflated to lock to the bone anchorsand stabilize the bone components. A deployment system, comprising adelivery catheter removably carrying the implantable device, isprovided, such that the procedure may be conducted in a percutaneous orminimally invasive manner to minimize procedure trauma to the patient.

The deployment system shown in FIG. 1 comprises a delivery catheter 100which deploys the implantable inflatable orthopedic device 102. Deliverycatheter 100 preferably includes an elongate, flexible tubular body 104,having a proximal end 106 and a distal end 108. For certainapplications, however, in which direct linear access is intended, thetubular body 104 may be substantially rigid. The tubular body 104includes one or more passages or lumens extending axially through thebody, depending upon the desired functionality of the device.

The overall length and cross sectional dimensions of the deliverycatheter 100 may be varied, depending upon the intended clinicalapplication. In a device intended for percutaneous or minimally invasivefusion of lumbar and/or sacral vertebrae, for example, the tubular body104 will generally have a length within the range of from about 15 cm toabout 50 cm, and a diameter within the range of from about 2 mm to about6 mm.

Percutaneous insertion of the delivery catheter 100 may be facilitatedby the provision of a removable elongate stiffening wire 122, extendingthrough a lumen such as inflation lumen 130 (see FIG. 2) from theproximal end 106 of tubular body 104, to the distal end 108 of tubularbody 104. Optionally, the stiffening wire 122 extends into, and even allthe way to the distal end 118 of the orthopedic device 102, to providesupport and column strength to the device 102 which may be desirableduring tissue penetration. The distal end of the stiffening wire 122 maybe connected to a coil approximately 8 cm in length to allow for adegree of flexibility.

FIG. 2 shows a cross-sectional view through the elongate body 104,showing (not to scale) an inner sleeve 110 and an outer sleeve 112. Theinner sleeve 110 defines a first, inflation lumen 130, while a second,venting lumen 132 is defined by the annular space between the innersleeve 110 and outer sleeve 112. The inflation lumen 130 is adapted toreceive the elongate stiffening wire 122 in a sliding fashion through aproximal opening 127 on inner sleeve 110, which in turn extends axiallyinto the outer sleeve 112 by way of port 126 in catheter manifold 124.Although the illustrated embodiment has a dual lumen, concentric orcoaxial configuration, three or more lumen may alternatively beprovided, depending upon the desired capabilities of the catheter. Asingle lumen catheter may also be provided, to accommodate a removablestiffening wire, if utilized, and to facilitate inflation of theimplantable device. Alternatively, a two or more lumen catheter shaftmay be fabricated, extruded or otherwise formed with the lumen in aside-by-side configuration.

The deployment device 100 further comprises a manifold 124, located atthe proximal end 106 of the elongate tubular body 104. The cathetermanifold 124 provides a maneuvering handle for the health careprofessional, and supports an inflation port 126 and a vent port 128.Either or both the inflation port 126 or the vent port 128 may beprovided with a coupling, such as a luer-lock fitting for connection toassociated devices as is known in the art. For example, a luer or otherconnector on the inflation port 126 facilitates connection to a sourceof pressurized inflation media in a conventional manner. The vent port128 may be connected to a syringe or other device to draw a vacuum, toevacuate air from the balloon prior to infusion of the hardenable media.

The manifold 124 may also include an injection port for allowinginjection of radiopaque contrast fluid to enable visualization of thedelivery device on a fluoroscope. The proximal manifold 124 may bemachined or injection molded of any of a variety of known suitablematerials such as PTFE, ABS, nylon, polyethylene, polycarbonate, orothers known in the art. A precision gasket may also be provided, whichseals securely around the inner sleeve 110, prohibiting fluid loss.

Catheter manufacturing techniques are generally known in the art,including extrusion and coextrusion, coating, adhesives, and molding.The catheter of the present invention is preferably made in aconventional manner. The elongate shaft of the catheter may be extruded,using polymers such as Nylon, PEBAX, PEEK, PTFE, PE or others known inthe catheter arts, the stiffness of which may be selected asappropriate. Material selection varies based on the desiredcharacteristics. The joints are preferably bonded. Biocompatibleadhesives or heat bonding may be used to bond the joints. The balloonand stent are also made in a conventional manner.

The deployment system 100 further comprises an implantable inflatableorthopedic device 102, which may function, in a spinal fusionapplication, as an inflatable or formed in place fixation plate or rod.Implantable device 102 is removably carried by the distal end of thetubular body 104, such that inflation lumen 130 is in communication withthe interior cavity 146 of the inflatable device 102. The inflationmedia may thus be infused through inflation port 126 (or opening 127)located at manifold 124 to fill the cavity 146.

The implantable device 102, which may be a balloon 114, includes aproximal end 116, a distal end 118, and a flexible wall 148. The balloon114 may be formed from any of a variety of polymeric materials which areknown in the balloon angioplasty arts. These include, for example,complaint materials such as polyethylene, polyethylene blends or nylon,and substantially noncompliant materials such as polyethyleneterephthalate. Any of a wide variety of other biocompatible polymers maybe utilized, as will be apparent to those of skill in the art in view ofthe disclosure herein.

The balloon 114 may comprise a single or multiple layers, depending uponthe desired physical properties. In one embodiment, the ballooncomprises two layers, having a reinforcing structure such as a stent ora plurality of axially extending support strips sandwiched therebetween.In an alternate embodiment, the balloon 114 comprises a first, innerlayer which restrains the hardenable media. A second, outer layer iscoaxially disposed about the first layer, and is provided with aplurality of apertures or a microporous structure. An infusion lumen isprovided in the elongate tubular body, for providing communicationbetween a proximal infusion port and the space in between the inner andouter balloon layers. In this manner, fluids, which may contain any of avariety of medications, can be infused into the tissue surrounding thetreatment site. Suitable structures and manufacturing considerations aredisclosed in U.S. Pat. No. 5,295,962 to Crocker et al., the disclosureof which is incorporated in its entirety herein by reference.

Although a cylindrical configuration for balloon 114 is illustratedherein, any of a variety of alternative cross sectional configurationsmay be utilized. The overall length, diameter and wall thickness of theimplantable inflatable orthopedic device 102 may be varied, depending onthe particular treatment and access site. In one embodiment, device 102has an inflated length between about 2 and 12 cm, and often betweenabout 5 cm and about 8 cm for adjacent vertebrae fixation. The device102 has an inflated diameter of generally between about 0.5 and 2 cm.

The length of the balloon 114 is based upon the anticipated distancebetween the first and second anchors, or, in an embodiment having morethan two anchors, between the anchors having the greatest axialseparation. For example, in a fusion application in which two adjacentlumbar vertebrae (e.g. L4-L5) are to be fused in an adult, the first andsecond anchors will generally be spaced apart by a distance within therange of from about 5 cm to about 8 cm. Preferably, the axial length ofthe balloon 114 is sufficiently longer than the inter anchor spacing topermit a portion of the balloon to expand on the “far” side of theanchor aperture as is illustrated, for example, in FIG. 9. Thus, balloonlengths for the above identified inter anchor distances will generallyexceed the sum of the inter anchor distance and the anchor diameters byat least about 0.5 cm. Preferably, the balloon extends at least about 1cm beyond the portals.

For use in an application where a first vertebrae is attached to asecond vertebrae, and the second vertebrae is separated from the firstvertebrae by at least a third vertebrae, for example in the lumbarspine, the inter anchor distance will generally be within the range offrom about 10 cm to about 20 cm. As will be appreciated by those ofskill in the art, in a three or more vertebrae fixation, theintermediate vertebrae or vertebraes will normally but need notnecessarily be connected to the inflatable balloon 114. Thus, in oneapplication, the balloon 114 connects a first attachment point at afirst bone and a second attachment point at a second bone, with one ormore intermediate bones unconnected to the balloon 114. In anotherapplication, at least a third anchor is provided in between the firstand second anchors, and the balloon 114 is threaded through an apertureon each of the first, second and third anchors. The desirability ofattaching or leaving unattached intervening vertebrae or other bones orstructures between two attachment points is a matter of clinicaljudgement, in view of the particular circumstances of the patient.

The primary function of the balloon 114 is to influence or control theshape of the hardenable media, following injection therein. Theimplantable balloon 114 is not normally required to restrain pressureover an extended period of time. Thus, a greater design flexibility maybe permitted, compared to conventional angioplasty or other dilatationballoons. For example, the balloon 114 may be porous, either for drugdelivery as has been discussed, or to permit osteoincorporation and/orsoft tissue ingrowth.

Certain hardenable media which may be utilized in connection with thepresent invention, such as PMMA, have a significantly greater viscosityin the precured form, compared to conventional angioplasty ballooninflation media. In addition, since the balloon 114 is not intended tocontain significant pressure, conventional high strength materials suchas for high pressure angioplasty may not be necessary. This allows theballoon 114 to be constructed in any of a variety of ways, includingtechniques utilized for balloon angioplasty applications. In addition,the balloon 114 (or balloon-like structure) may be made out of any of awide variety of woven or nonwoven fibers, fabrics, metal mesh such aswoven or braided wires, and carbon. Biocompatible fabrics or sheetmaterial such as ePTFE and Dacron® may also be used.

The hardenable media is preferably a rapid setting, liquid polymer orpolymer precursor, such as polymethyl methacrylate. However, any of avariety of other materials which provide the required stiffening orsetting characteristics may be used, including any of a variety ofepoxies, polyurethane or blends of polyurethane-silicone.

In the context of a rod shaped inflatable container, for use in spinalfixation procedures, the physical requirements of the hardenable mediawill depend upon the length and diameter of the rod as well as thephysical requirements imposed by the implantation site. For certainembodiments, polymethyl methacrylate, epoxy, polyurethane or otherparticular material may or may not exhibit sufficient physicalproperties. Physical properties of hardenable materials can be modifiedthrough the addition of any of a variety of additives, such as carbonfibers, Kevlar or Titanium Rods, woven or laser etched metallic tubularstents, or other strength enhancers as will be understood in the art.The selection of a particular hardenable media, as well as thedesirability of adding strength, flexibility, or other physical propertyenhancers, can be optimized for any particular implantation systemthrough routine experimentation by those of skill in the art in view ofthe disclosure herein.

Certain composite materials, such as carbon fibers embedded in a bondingagent such as a two part epoxy, or two part polyurethane have been foundparticularly useful in forming the implant of the present invention. Forexample, graphite (carbon fibers) having a diameter within the range offrom about 0.003 to about 0.007 inches are provided in bundles (tows)composed of from about 3,000 to about 12,000 fibers. One typical fiberuseful for this purpose is manufactured by Hexcel Carbon Fibers, SaltLake City, Utah, Part No. HS/CP-5000/IM7-GP 12K. Preferably, the Towtensile strength is in the range of from about 5,000 to about 7,000 Mpa.Tow tensile modulus is within the range of from about 250 to about 350Gpa.

In general, the composite rods in accordance with the present inventionwill exhibit a static compression bending values (per ASTM F1717) withinthe range of from about 100 to about 200 lbs., and, preferably greaterthan about 150 lbs. The composite rods will exhibit a static torsion(per ASTM F1717) within the range of from about 300 to about 500 inchpounds, and, generally in excess of about 400 inch pounds. The rods willpreferably reach at least about 5 million cycles, at 5 Hz. Each of theseparameters may be measured in accordance with the protocols described inthe American Society for Testing and Materials (ASTM) designation F1717-96, a copy of which is attached hereto as Appendix A, and which isincorporated in its entirety herein by reference.

Within the range of from about 30 to about 60 bundles of the carbonfiber described above is packed in a deflated balloon, optionally alongwith a Ni—Ti stent having an 8 mm diameter and 8 cm length. Although anyof a variety of stents may be utilized, one useful structure is similarto the Smart Stent (Cordis), and it helps keep the structure intact andalso adds structural strength to the implanted structure.

A one or a two part-epoxy having a viscosity in the range of from about100 to about 500 cps is then-injected into the balloon under pressuresuch as by using a pump and pressure within the range of from about 4ATM to about 10 ATM or more depending upon viscosity, balloon strengthand other design considerations. The pump is run for a sufficientduration and under a sufficient pressure to ensure that the epoxy wetsall of the fibers. This may range from about 10 minutes or more to aboutan hour, and, in one application where the pump was run at about 5 ATMpressure, requires at least about ½ hour. Specific method parameters maybe optimized depending upon the viscosity of the epoxy, infusionpressure, infusion flow rate, density of the packed carbon fibers, andother variables as will be apparent to those of skill in the art in viewof the disclosure herein.

In an alternate embodiment, carbon fibers having within the range offrom about to about 45 degrees of braids are utilized. The braid may bein the form of a plain weave, and may be obtained, for example, fromComposite Structures Technology (Tehachapi, Calif.). A 0.5 inch diameterof 45 degrees braided carbon fiber sleeve is positioned within thecenter of the balloon. This braided sleeve conforms dimensionally to theinside diameter of the balloon. A 0.3 inch diameter braided carbonsleeve (again 45°×45° plain weave) may also be positioned concentricallywithin the balloon, within the outer braided carbon fiber sleeve.Unidirectional fibers are thereafter introduced inside of the ID of theinner braided carbon sleeve. Unidirectional fibers are also introducedinto the annular gap between the two braided sleeves. The volume of thefiber per volume of balloon is generally within the range of from about40% to about 55%. After placement of the foregoing structure within theportals of the screws, the epoxy mix having a viscosity within the rangeof from about 100 to about 500 cps is injected under 10 atmospherespressure into the balloon.

Although the foregoing composite structure was described using a carbonfiber example, any of a variety of fibers may be positioned within theballoon to enhance the physical properties of the finished product. Forexample, Kevlar fibers, PEEK, and any of a variety of alternatives maybe used. In general, the fibers will preferably provide a very hightensile strength and high modulus, having a low diameter to enhancedeliverability of the device.

The use of braided sleeves will produce higher structural resistance tosheer stress as a result of torsional loads, plus the ability todistribute unidirectional fibers in a homogenous manner within theballoon at all times. This appears to improve the performance of theimplant.

One construction of a composite formable rod in accordance with thepresent invention is illustrated in FIG. 4C. An outer balloon or othercontainment structure 114 is provided, as has been discussed. Areinforcing element 120 such as a stent is concentrically positionedwithin the balloon. An outer support tube 121 is positioned within thestent in the illustrated embodiment, however, the outer support tube 121can alternatively be positioned concentrically outside of the stent 120.The outer support tube 121, in one embodiment, is a 0.5 inch diameterbraided carbon fiber tube, having cross strands oriented at 45° angleswith respect to each other to improve torsion resistance as has beendiscussed.

An inner support tube 123 is spaced radially inwardly from the outersupport tube 121. Inner support tube 123, in one embodiment, comprises a0.3″ diameter braided carbon fiber sleeve having characteristicsdescribed above. A first plurality of unidirectional fibers 125 isaxially oriented within the annular space between the outer support tube121 and inner support tube 123. A second plurality of unidirectionalcarbon fibers 127 is positioned within the inner support tube 123.

Any of a variety of alternate constructions can be readily utilized, inaccordance with the teachings herein. For example, three or more tubularsupport tubes may be utilized. The layering sequence of the variouscomponents may be changed, and other features added or deleted dependingupon the desired performance of the finished device. In addition,although the balloon 114 in one embodiment comprises a nylon singlelayer balloon, other materials may be utilized. In addition, multiplelayer balloons may be utilized, with or without support structures suchas stents, wires, or woven tubular support structures sandwichedtherebetween.

Marker bands made of materials such as gold, platinum or tantalum mayalso be positioned on the balloon, to facilitate fluoroscopicvisualization. Alternatively, a radio opaque material, such as tantalumpowder, may be sprinkled among the carbon fibers prior to infusion ofthe epoxy or other hardenable media, to allow visualization duringplacement.

The epoxy or the polyurethane material preferably has a relatively fastcure rate at 37° C. A low viscosity (no greater than from about 100 toabout 1000 CPS) facilitates rapid transluminal introduction through thedelivery catheter and wetting of the relatively small interstitialspaces between adjacent carbon fibers. In addition, the polymer ispreferably radiopaque. The polymerization is preferably minimallyexothermic, to minimize or prevent thermal damage to the surroundingtissue. One epoxy which may be useful in the present invention is Epotek301 available from Epoxy Technologies. This epoxy reaches 50 to 60% ofits strength within about three to four hours following deployment, at37° C. Using a bonding agent having these approximate characteristics,the patient can be restrained from rolling for an initial cure period ofapproximately three or four hours to achieve a partial cure (e.g., atleast about 50% and preferably 60% or more), and be maintained in bedfor a secondary cure period such as approximately the next eight totwelve hours or more to accommodate a full cure. Other formulations oftwo part epoxies or polyurethanes with faster cure times (preferably nomore than about one hour full cure) can be formulated by changing theratios of components and formulations for the catalysts. Cure time canalso be accelerated through the use of accelerators, such as catalystsor the application of heat as is discussed in detail below.

Terms such as “hardenable” or “curable” media are used interchangeablyherein, and are intended to include any material which can betransluminally introduced through the catheter body into the cavity 146while in a first, flowable form, and transitionable into a second,hardened form. These terms are intended to cover materials regardless ofthe mechanism of hardening. As will be understood by those of skill inthe art, a variety of hardening mechanisms may exist, depending uponmedia selection, including UV, other wavelength of electromagneticenergy, or catalyst initiated polymerization, thermally initiatedpolymerization, solvent volatilization, and the like. While the mediaselection may affect catheter design in manners well understood by thoseof skill in the art, such as to accommodate outgasing of byproducts,application of heat, catalysts, or other initiating or acceleratinginfluences, these variations do not depart from the concept of theinvention of introducing a flowable media into a shape and subsequentlycuring the media to the shape. Two part medias, such as a two part epoxyor polyurethane, or a monomer and an initiator may be introduced intothe cavity 146 through separate lumen extending throughout the tubularbody. Expandable media may also be provided, such as a material which isimplantable in a first, reduced volume, and which is subsequentlyenlargeable to a second, enlarged volume such as by the application ofwater or heat, or the removal of a restraint.

Various safety features to minimize the risk of rupture or leakage ofthe hardenable media may be utilized, depending upon design preferences.For example, a two-layer or three-layer or more balloon may be utilizedto reduce the risk of rupture. In addition, the material of the singleor multiple layers of the balloon may be selected to minimize escape ofvolatile components from the curable media. In one embodiment, a doubleballoon is provided having a nylon inside layer and a PET outside layer.

In addition, the inflation pressure of the curable media may be affectedby the nature of the balloon. For example, a polyethylene balloon havinga wall thickness of about 0.001″ may have a burst pressure of about 7 to8 atmospheres. In that embodiment, an inflation pressure of no more thanabout 4 to 5 atmospheres may be desired. A slightly higher inflationpressure, such as on the order of from about 5 to about 6 atmospheres,may be utilized with a nylon balloon. Relatively noncompliant materialssuch as PET have much higher burst pressures (range of 10-20atmospheres), as is well understood in the balloon angioplasty arts.

In addition, the balloon contains a proximal valve as will be discussedin additional detail below. Multiple valves may be utilized, in seriesalong the flow path, to reduce the risk of failure and escape ofhardenable media. As a further safety feature, the deployment cathetermay be provided with an outer spill sheath in the form of an elongateflexible tubular body which surrounds the deployment catheter and atleast a proximal portion of the balloon. This spill sheath provides anadditional removable barrier between the junction of the catheter andthe balloon, and the patient. If a spill occurs during the fillingprocess, the spill sheath will retain any escaped hardenable media, andthe entire assembly can be proximally retracted from the patient.Following a successful filling of the balloon, the spill sheath anddeployment catheter can be proximally retracted from the patient,leaving the inflated formable orthopedic fixation structure in place.

The reinforcing element 120 may be exposed to the interior cavity 146formed by the flexible wall 148, providing additional structuralintegrity. See, e.g., FIGS. 1 and 4C. The reinforcing element 120resists kinking of the balloon as the balloon is advanced around cornerssuch as during advancement through an aperture (e.g., portal or eyelet)on a bone anchor. The reinforcing element 120 may be positioned withinthe balloon 114. The reinforcing element may alternatively be embeddedwithin the wall of the balloon 114, or carried on the outside of theballoon much like a conventional stent. The reinforcing element 120 maybe an expandable tube, a slotted metal tube, reinforcing wires,straight, woven or braided fibers such as carbon fibers, or a stent andmay be provided with electrical conductors for completing a circuitthrough the deployment catheter, to generate heat and/or measuretemperature, as is discussed below. Certain preferred embodiments mayinclude a tube or wire. Reinforcement element 120 may comprise thin,reinforcing metallic wires, separate from the balloon wall. The wiresincrease the tensile strength of balloon 114 when inflated. Wires may betitanium, nitinol, elgiloy, or any other suitable material as known tothose of skill in the art.

The reinforcement element 120 may include an expandable tubular stent. Astent of any suitable type or configuration may be provided with thedelivery device, such as the Cordis artery stent (“smart stent”).Various kinds and types of stents are available in the market(Sulzer/Medica “Protege” stent and Bard “Memotherm” stent), and manydifferent currently available stents are acceptable for use in thepresent invention, as well as new stents which may be developed in thefuture.

Referring to FIGS. 4A and 4B, the illustrated elongate tubular body 104comprises an outer sleeve 112 and an inner sleeve 110 movably positionedwithin the outer sleeve 112. The inflatable device 102 is removablycarried by or near the distal end 108 of the outer sleeve 112.Alternatively, the inflatable device 102 may be removably carried by theinner sleeve 110. The inner sleeve 110 may extend into the inflatabledevice 102, as illustrated.

The balloon 114 may be removably attached to the tubular body 104 by aslip or friction fit on the distal end 108 of the outer sleeve 112 or onthe inner sleeve 110. A variety of alternative releasable attachmentsmay be used between the outer sleeve 112 and/or inner sleeve 110 and theproximal end 103 of the balloon 114, such as threaded engagement,bayonet mounts, quick twist engagements like a luer lock connector, andothers known in the art. In each of these embodiments, a first retentionsurface or structure on the outer sleeve 112 and/or inner sleeve 110releasably engages a complimentary surface or retention structure on theproximal end 103 of the balloon 114 as will be apparent to those ofskill in the art.

The balloon 114 comprises a self-sealing valve 160 which prevents thehardenable media from leaking once the delivery catheter 100 is detachedfrom the balloon 114. Valve 160 is provided for closing the pathwaybetween inflation lumen 130 and inner cavity 146. Valve 160 may belocated at the proximal end 116 of inflatable device 102. A variety ofdifferent valves may be used as will be recognized by those of skill inthe art, such as a slit valve, check valve, duck-billed or flap valve.Alternatively, a stopper may be provided which can be placed within thepathway to prevent leakage.

Referring to FIG. 7A, a duck bill valve is schematically illustrated.This valve includes at least a first, and preferably two or morecoaptive leaflets 161 and 163, which incline towards each other in thedistal direction as will be understood by those of skill in the art.Distal advancement of the inner sleeve 110 and/or pressurized mediathrough the valve 160 forces the coaptive leaflets 161 and 163 apart, tofacilitate introduction of the hardenable media. Upon removal of theinner sleeve 110, the coaptive leaflets 161 and 163 return to a closedconfiguration to inhibit or prevent the escape of hardenable media. Asingle leaflet 161 may be utilized, in the form of a flapper valve.

An alternate valve is illustrated in FIGS. 7B and 7C, and in anassembled device in FIG. 4B. In this valve, a tubular support structure165 is provided with a closeable cap 167. The closeable cap 167 may beformed from any of a variety of highly flexible polymeric materials,such as silicone, neoprene, latex, or others known in the art. Cap 167may be formed such as by dip molding or liquid injection molding,followed by the provision of a slit or potential opening 169.

The valve 160 may be connected to or formed with the inflatable devicein any of a variety of manners, as will be appreciated in view of thedisclosure herein. In the illustrated embodiment, the balloon 114 isprovided with a proximally extending neck 115 which carries the valve160 therein. The tubular body 165 having the cap 167 thereon ispositioned concentrically within the proximal neck 115, as illustratedin FIG. 4B. Alternatively, the valve 160 may be positioned within theballoon 114, i.e., distally of the proximal shoulder of the balloon 114.

Additional details of one detachable connection between the deliverysystem and the implantable device is illustrated in FIG. 4B. Asillustrated therein, a tube 161 extends distally from the outer sleeve112. Tube 161 may comprise any of a variety of materials, which exhibitsufficient structural integrity for the intended use. In one embodiment,tube 161 is a metal hypotube having an inside diameter of about 0.085″to about 0.086 and a wall thickness of about 0.001″ to about 002″. Thetube 161 in the illustrative embodiment extends for a distance of about0.50 mm to about 0.75 mm beyond the distal end of the outer sleeve 112.

The tube 161 extends into a sliding fit with a tubular support structure163 which may be positioned in a proximal neck portion of the balloon.When positioned as illustrated, the tube 161 ensures that the valve 160is open, so that the inner sleeve 110 may extend axially therethroughinto the balloon.

In addition, the inside diameter of the tube 161 is preferablysufficiently larger than the outside diameter of the inner sleeve 110 toprovide an annular passageway in communication with the vent lumen 132.This structure ensures that the interior of the balloon remains incommunication with the proximal vent port by way of a vent lumen 132extending throughout the length of the assembly. In the illustratedembodiment, the outside diameter of the inner sleeve 110 is about 0.082″to about 0.084″, and the inside diameter of the tube 161 is about 0.085″to about 0.086″. Following infusion of the curable media into theballoon, the inner tube 110 and tubular body 161 are both proximallyretracted from the balloon, thereby enabling the valve 160 to close asis described elsewhere herein.

When fully inflated, as shown in FIG. 6, the balloon 114 has an inflatedprofile with a cylindrical working portion 140 having an inflateddiameter located between a pair of conical end portions 142, 144.

Referring to FIG. 9, at least one bone anchor 10 may be provided, suchas that shown in FIG. 10. The bone anchor 10 includes a first aperture22, through which the orthopedic device 102 extends. A second boneanchor 10 may also be provided including a second aperture 22, throughwhich the orthopedic device 102 also extends. The first bone anchor 10is preferably implanted within a first bone. The second bone anchor 10may be implanted within the second bone. The bones may be adjacentvertebrae or first and second vertebrae spaced apart by one or two ormore intermediate vertebrae.

The bone anchors of FIGS. 10-13 are made of a biocompatible materialsuch as titanium or stainless steel. Alternatively, bone anchors 10 maybe made of a composite material. Bone anchors 10 may also be made of asuitable medical grade polymer. In one embodiment, bone anchors 10 havea length between about 40 mm and 60 mm, preferably about 50 mm. However,the actual length is dependent on location of the fracture, size ofpatient, etc.

Bone anchor 10 comprises a proximal portion 12 having a proximal end 14and a distal portion 16 having a distal end 18. Proximal portion 12typically comprises a head and a portal 22. In a preferred embodiment,head 20 comprises a proximal portion 24 configured to mate with the tipof a screwdriver. Head 20 may comprise a standard or Phillips slot formating with the screwdriver. A variety of slot configurations are alsosuitable; such as hexagonal, Torx, rectangular, triangular, curved, orany other suitable shape. The bone anchor of FIG. 13 has a raisedplatform 25 having a plurality of substantially straight sides, such asa hexagonal platform, configured to mate with a corresponding depressionin the distal end of a screwdriver. Platform 25 may come in a variety ofshapes suitable mating with a screwdriver.

Portal 22 of bone anchor 10 may extend through head 20 and is generallybetween about 4 mm and 8 mm in diameter, preferably about 6 mm to about8 mm in diameter. Portal 22 may be of any shape suitable for receivinginflatable, implantable orthopedic device 102; however, portal 22 ispreferably round.

Distal portion 16 of bone anchor 10 typically comprises threads 26 and asharp tip 28. Bone anchor 10 also preferably comprises a central lumen30 extending coaxially completely through bone anchor 10 from proximalend 14 to distal end 18 and configured to receive a guidewire. Boneanchor 10 may also include at least one perforation 32, as shown in FIG.13. Perforation 32 may be aligned axially, as shown, or may be staggeredaxially. Perforation 32 permits bone to grow into bone anchor 10,stabilizing bone anchor 10 within the bone. Additionally, bone matrixmaterial such as a hydroxyapatite preparation can be injected intocentral lumen 30 and through perforation 32 to promote bone in-growth.

FIGS. 14 and 15 show screwdrivers 40 configured to apply torque to boneanchor 10. Screwdriver 40 comprises a proximal portion 42 having aproximal end 44 and a distal portion 46 having a distal end 48. Proximalportion 42 includes a handle 50 configured to permit grasping to applytorque to anchor 10. Various configurations of proximal end 44 arepossible. In the embodiment of FIG. 15, the proximal handles 50 may beindependently rotatable about their longitudinal axes.

Distal portion 46 comprises a shaft 52 having a tip 54 configured tointerface with proximal portion of bone anchor 10. Screwdriver 40 mayalso comprise a central lumen 55 extending coaxially from proximal end44 to distal end 48 configured to receive a guidewire.

FIG. 16 shows a guidewire directing device 60, which may be usedpercutaneously to alter the direction of an advancing guidewire.Guidewire directing device 60 comprises a proximal portion 62 having aproximal end 64 and a distal portion 66 having a distal end 68. Proximalportion 62 comprises a handle 70. Handle 70 is configured to assist ingrasping and manipulating guidewire directing device 60. The distalportion 66 comprises a shaft 72 having a fork-tipped end 68. Guidewiredirecting device 60 engages a guidewire at the fork-tipped end 68.Handle 70 is rotated, advanced, and withdrawn, thereby altering thedirection of the advancing guidewire.

A directing sheath 180, as shown in FIG. 17, may also be provided forassisting in aligning the guidewire or delivery catheter to pass throughbone anchors 10. Directing sheath 180 comprises a proximal portion 182,a distal portion 184, and a central portion 186. Central portion 186includes at least two openings 188 sized substantially the same asportal 22 of bone anchor 10. Directing sheath 180 preferably includes alumen 190 extending through its entire length. Lumen 190 is ofsufficient diameter to allow a structure such as a guidewire or deliverycatheter to pass through. Directing sheath 180 may be scored along itslongitudinal axis, on either one line or two opposing lines 192. Scoring192 allows directing sheath 180 to be split into two separate halves bypulling the sheath apart at its proximal or distal end. Scoring 192 canbe partially or completely through the sheath wall.

Directing sheath 180 is preferably formed from a biocompatible polymer.Directing sheath 180 may also include a radiopaque filament 194 passingaround each opening in central portion 186 or the entire length ofsheath 180. Filament 194 aids in localizing directing sheath 180 afterpercutaneous placement.

FIG. 44 illustrates the structure of an accelerator for accelerating thecuring of the curable media in one embodiment of the invention. In thisembodiment, the accelerator comprises a heating coil 300 within thedevice 102 such as concentrically around the distal end of the innersleeve 110 of the elongate tubular body 104 of a delivery catheter 100.While the heating coil 300 is shown coiled around the exterior surfaceof the distal end of the inner sleeve 110, it can also be fitted insidethe distal end of the inner sleeve 110, or embedded within the distalend of the inner sleeve 110. The distal portion of the sleeve 110 may beprovided with a detachable joint at the proximal end 116 of the balloon114 such that it is left behind within the implantable device 102following removal of the delivery catheter 100. A variety of releasableattachments may be used, such as threaded engagements, bayonet mounts,quick twist engagements like luer lock connectors, or others known inthe art.

The accelerator is not necessary a part of the delivery catheter 100.FIG. 45 schematically illustrates another embodiment in which theaccelerator is built into the inflatable orthopedic device 102. Asdisclosed above, a variety of structures may be provided asreinforcement element 120 in the cavity 146 of the balloon 114, such ascarbon fibers, titanium rods, or tubular stents. If the reinforcementelement 120 is made from electrically conductive materials, it can alsofunction as a resistive heating element. In FIG. 45 a metallic stent isillustrated. Titanium rods and carbon fibers may also be used.Electrical contacts 310 and 312 for conducting a current through thereinforcement element 120 are incorporated into the releasableattachment, such as a concentric sliding fit connection, used betweenthe outer sleeve 112 and/or inner sleeve 110 and the proximal end 103 ofthe balloon 114. These electrical contacts engage complimentary contactson the outer sleeve 112 and/or inner sleeve 110 to complete an electriccircuit with a proximally located power supply for running the resistiveheating element.

In order to accomplish the objective of accelerating polymerization ofthe epoxy or other hardenable media, the heating element preferablyelevates the temperature of the epoxy to a point above normal bodytemperature. Temperatures at the heating element of at least about 43°,preferably at least about 50°, and, under certain circumstances as highas 60° C. or more are desirable to produce an optimal cure rate.However, the outside of the implant is preferably not heated to theextent that it causes localized tissue necrosis. Tissue necrosis occursat approximately 45° C. Thus, the heat source preferably sets up atemperature differential between the surface of the implant and theinterior of the implant. This may be accomplished in several ways, suchas, for example, selecting materials and thickness of the outer flexiblewall 148 to provide thermal insulation of the adjacent tissue from heatgenerated by the heating element. As an alternative or in addition, heatsink structures may be provided at or near the outer surface of theorthopedic device 102. A flow path such as an annular space formedwithin a double walled balloon may be utilized to circulate a coolantsuch as saline or other circulating cooling fluid. Such measurespreferably permit the heating element to be heated as high as 50° C. orhigher, while maintaining the outside surface of the device 102 at atemperature of no more than about 45° C., and, preferably no more thanabout 43° C.

Excessive temperature can also be reached transiently, such as at thebeginning of a heating cycle when the temperature may temporarilyovershoot the 45° C. desired maximum. The present inventors havedetermined that the initial temperature overshoot can be eliminated orreduced by appropriately driving the power to the heating element as isdiscussed in detail below. The driver circuitry preferably brings theheating element up to operating temperature rapidly, while minimizingthe risk of thermal overshoot beyond a predetermined maximum. All of theforegoing measures preferably allow a sufficient curing of thehardenable media to limit the required period of immobility to no morethan about 2 hours, preferably no more than about 1 hour and, optimallyno more than about 45 minutes post implantation. Although a completecure is not required within this time window, a sufficient cure isdesirable that the patient need not be immobilized beyond the initialcure. Thereafter, the hardenable media will continue to harden, such asover the next few hours or even days, but with little or no restrictionon the patient's activities.

The resistive heating element, whether the heating coil 300, thereinforcement element 120, or other structure, may be made from materialwith either a positive or negative temperature coefficient ofresistance, e.g., electrical resistance either directly or indirectlyproportionate to temperature, respectively. The temperature may bemonitored by measuring the DC voltage across the resistive heatingelement, for the voltage is directly proportional to resistance for agiven current, and the temperature coefficient of resistance is known.Alternatively, by measuring the voltage, current and phase of the drivesystem, the resistance of the heating element and thus its temperaturecan be calculated by a microprocessor or dedicated circuitry.

Alternatively a thermistor 314 may be used to monitor the temperature ofthe inflatable orthopedic device 102. Thermistors are well known in theart. Using one or more separate thermistors 314 would entail moreelectrical contacts (not shown) as another electrical loop in additionto the one running the heating element may be necessary. Other methodsof measuring the temperature include the use of an optical fiber inconjunction with a thermally reactive material, a coaxial plunger inconjunction with a thermal bulb, or a semiconductor temperature sensoror junction (such as a diode) carried by the orthopedic implant. Abimetallic heating element may function similarly to a circuit breakerand self-regulate.

FIG. 46 illustrates one embodiment of the control panel 316 for theheating element 300, in electrical communication with catheter manifold124. The heating cycle selected and the time elapsed/remaining in thecycle are displayed. Each heating cycle is associated with a heatingprofile, a table of target temperatures at different points of time inthe heating cycle. A button may be used to toggle the display betweenelapsed and remaining time. There is also a power switch, a selector forthe heating cycle, and a run/pause button to interrupt the heatingcycle. LED's or other indicators may be used to indicate whether theheating cycle is running or paused. LED's may also be used to indicatethe status of the battery—low, charging or full, the status of thecontrol block—on or off, and the status of the heating element—heatingor not. The heating indicator is preferably configured to light when theheating element is first active, and blink when the temperature of theheating element is regulated via the heating profile. Ideally thecontrol block 324 is provided with circuitry that detects faults andproblems with the connection. These problems may be communicated to theuser via LED's and/or audible alarms.

The illustrated embodiment of the control panel 316 has a cycle button600 with which to select the heating cycle, and a cycle window 602 todisplay the cycle selected. The control panel 316 is also provided witha pause switch 604 to pause the heating cycle, and LED's 606 and 608respectively to indicate whether the cycle is running or paused. A timewindow 610 indicates the time elapsed in the heating cycle. An optionaltoggle switch (not shown) may be used to toggle the time window 610 todisplay the time remaining in the heating cycle. A power switch 612turns the control panel on and off while a power LED 614 displays itspower status. A heating LED 616 indicates whether the heating cycle isin a heating phase. Warning LED's 618 indicate whether there is a faultin the circuitry or connection with the heating element 300. BatteryLED's indicate the charge status of the battery.

FIG. 47 is a simple block diagram of a control circuitry of the heatingelement in one embodiment. This circuit allows optimization of theheating cycle, by heating the heating element rapidly to the desiredtemperature but minimizing the risk of a thermal overshoot beyond thetarget temperature which would have created a risk of thermally inducednecrosis. A start switch 320 begins a heating cycle and a timer 322. Acontrol block 324, controlled via the control panel 316, stores aheating profile and controls the circuitry described below. Aprogrammable pulse width modulated power source is used as a highfrequency power generator 326 to supply power, through a high-passfilter 328 to the heating element 330. The high frequency powergenerator 326 ideally operates at a frequency above the biologicalbandwidth. While any circuitry operating at frequencies above 2 kHzwould fit this description, frequencies above 10 kHz are preferable. Inone embodiment the high frequency power generator 326 operates at 125kHz, and in another it operates at 128 kHz.

Low-pass filters 332 isolate the high frequency power generator 326 froma precision current source 334 and an amplifier 336. The precisioncurrent source 334 feeds a low precise DC current through the heatingelement 330. The resulting DC voltage across the heating element 330 isamplified by the amplifier 336 and compared against a reference voltagegenerated by a reference module 338. The comparison is done by a levelcomparator 340. As voltage is directly proportionate to resistance at agiven current, the resistance across the heating element 330 can thus bemeasured. With the temperature coefficient of resistance of the heatingelement 330, the temperature of the heating element 330 can thus becalculated. The control block 324 acts on feedback from the comparator340 to enable or disable the high frequency power generator 326, andthus regulate the temperature of the heating element 330 according tothe heating profile. In one embodiment a clinical practitioner may havethe option of overriding the heating profile by inputting the desiredtemperature into the control block 324 directly.

While a resistive heat source has been described in some of the aboveembodiments, other energy sources to accelerate the curing of thecurable media may be used. These include, but are not limited to, addinga polymerizing agent, radio frequency, ultrasound, microwave and lasers.Also, the complete curing of the curable media by the describedapparatus and methods is not always required to occur beforediscontinuing the heat source or other initiator step in theseembodiments. When the curable media has been partially cured to acertain level of structural integrity, the patient does not have to beretrained for the remaining cure time necessary to achieve a completecure. Thus the period of patient immobilization is minimized using thecuring accelerators of the present invention.

Another specific embodiment is described in connection with FIGS. 48through 51. Although certain specific materials and dimensions will bedisclosed below, these are exemplary only and may be varied as will beunderstood by those of skill in the art. FIG. 48 a is an overview of aheated inflatable orthopedic balloon 400. The distal end 402 of theballoon 400 is sealed with a silicone adhesive. This silicone adhesivealso holds the distal marker 404 in place. The distal marker 404 may bemade of various materials, including gold, platinum or tantalum. Aninner tubing 406, made of PET, runs from the distal tip 402 along theaxis of the balloon 400 to the proximal end. The inner tubing 406 isporous, to allow the curable media to flow radially outwardlytherethrough. A heating element 408, such as a coated tungsten wire, iscoiled around the inner tubing 406. In the illustrated embodiment, theheating element 408 is coiled in a parallel double-stranded fashionaround the inner tubing 406, with the two strands joined in a loop 410towards the distal end 402 to form a continuous electrical pathway.Carbon fibers are provided in the space 412 between the inner tubing 406and the outer wall 414 of the balloon 400. The carbon fibers may have adiameter of between 0.003 to 0.007 inches. They are bundled in tows ofabout 3,000 to about 12,000 fibers. A typical carbon fiber suitable forsuch use is made by Hexcel Carbon Fibers, Salt Lake City, Utah, Part No.HS/CP-5000/IM7-GP 12K. Tow tensile strength in the range of about 5,000to about 7,000 Mpa may be achieved. Tow tensile modulus may be withinthe range of about 250 to 350 Gpa.

FIG. 48 b is an enlarged view on the proximal portion of the balloon400. The inner tubing 406 terminates at about the proximal end 416 ofthe balloon 400. The proximal end 416 comprises a nylon tubular supportstructure 417. Both the proximal marker 418 and the valve assembly 420are held in place in the tubular support 417 by a silicone adhesive. Twoconcentric electrical connector rings are also supported by the supportstructure 417. The inner electrical connector ring 422 is smaller indiameter, and located more distally, than the outer electrical connectorring 424. Each end of the heating element 408 is electrically joined toone of these electrical connector rings. A seal 426 is provided at theproximal tip of the tubular support 417. The proximal end 416 is shapedwith an-annular reduction in diameter such that a bottleneck 428 isformed just distal of the seal 426.

FIG. 48 c is an end view of the proximal end 416 along the axis of theballoon 400.

FIG. 49 is an enlarged view of the distal end of the catheter, with theballoon 400 removed. The innermost tube is the injection tube 430. Thelumen therein is the injection lumen 432. The injection lumen 432extends proximally to an injection port on the proximal end of thecatheter. The injection tube 430 is coaxially arranged within thesuction tube 434. An annular space between the outside surface of theinjection tube 430 and the inside surface of the suction tube 434defines the suction lumen 436. The suction lumen 436 communicates with asuction port on the proximal end of the catheter.

The inner electrical connector tube 438 is coaxially carried by theexterior perimeter of the suction tube 434. The outer electricalconnector tube 440 is coaxially arranged around the exterior perimeterof the inner electrical connector tube 438. A layer of electricalinsulation is provided between the two electrical connector tubes 438and 440. This can be accomplished by coating the inner surface of theouter electrical connector tube 440 or the outer surface of a proximalportion of the inner electrical connector tube 438 with an electricallyinsulating material, such as polyurethane or PTFE. Both electricalconnector tubes 438 and 440 may be slotted to ease connection, asdiscussed below. A wire connects each electrical connector tube to thedrive circuit of the heating element 408. Each electrical connector tubemay have an additional wire connected to it, which may be used togetheras a dedicated feedback loop to more accurately measure the electricalresistance of the heating element 408. A spacer tube 442 is providedwith a notch 443 which provides an annular seat for the proximal end ofthe outer electrical connector 440, to hold the outer electricalconnector tube 440 in place.

A lock tube 444 is coaxially arranged around the exterior perimeter ofthe spacer tube 442. The lock tube 444 is provided with one or two ormore axially extending slits 445 and provided with a radially inwardlyextending projection 446 for releasable engagement with a correspondingannular recess on the proximal end of the balloon 400, as discussedbelow. The inner tube 448 holds the suction tube 434 and the injectiontube 430, as all three extend all the way proximally into the catheterhandle. The outer tube 450 terminates proximally at a luer lock at thedistal end of the catheter handle.

FIG. 50 illustrates the proximal connections of the injection tube 430,the suction tube 434, the inner tube 448 and the outer tube 450 to thecatheter handle 500. As discussed above, the injection tube 430 isconnected to an injection port 502. The suction lumen 436, defined bythe space between the injection tube 430 and the suction tube 434, opensinto the suction port 504. The inner tube 448 extends into the catheterhandle 500, while the outer tube 450 terminates at a luer lock 506 atthe distal end of the catheter handle 500. The wires connecting theelectrical connector tubes 438 and 440 are routed through an electricalport 508. A luer lock 510 allows both injection tube 430 and suctiontube 434 to be removed from the catheter following injection of acurable medium into the balloon 400, as will be discussed below.

Referring to FIGS. 48 a, 48 b, 49, and 50, the attachment of thecatheter to the balloon 400 is now described. As described above, theinjection tube 430 and the suction tube 434 of the catheter are coaxial,with the injection tube 430 inside the suction tube 434. The injectiontube 430 extends through the inner tubing 406 into or close to thedistal end 402 of the balloon 400. The suction tube 434 extends throughthe valve assembly 420 of the balloon 400 to a point just distal of theproximal marker 418. The valve assembly 420 thus seals around theexterior surface of the suction tube 434.

When the catheter is attached to the balloon 400, the inner electricalconnector tube 438 contacts the inner electrical connector ring 422, andthe outer electrical connector tube 440 contacts the outer electricalconnector ring 424. As described above, both electrical connector tubesare slotted to ease their insertion into the respective electricalconnector rings. These two contacts complete the electric circuitbetween the heating element 408 and its drive circuitry.

The lock tube 444 holds the balloon 400 in place at the end of thecatheter. A seal 426 at the proximal end 416 of the balloon 400 sealsagainst the interior surface of the lock tube 444. As described above,the lock tube 444 is slit to ease its insertion over the proximal end416 of the balloon 400. One or more radially inwardly extendingprojections 446 provided on the interior surface of the lock tube 444complements the bottleneck 428 in the proximal end 416 of the balloon400 to provide an interference engagement which is maintained by theouter tube 450. The outer tube 450 may be released via the luer lock506, allowing it to slide distally over the lock tube 444 to restrainthe projection 446 of the lock tube 444 within the bottleneck 428 of theballoon 400.

Any of a variety of releasable connectors may be utilized, between thecatheter and the implant. For example, threaded connections, twistlocks, interference fit and friction fit structures are well known inthe art. In general, a releasable connection which will withstandsufficient tension and compression during the positioning process ispreferred. Such structures will generally include an interference fit.In the illustrated embodiment, a radially inwardly extending annularridge which is provided with two or more axially extending slots toallow lateral movement cooperates with a radially inwardly extendingannular recess on the proximal end of the implant as has been discussed.The radially inwardly extending ridge provides an interference surface,which may also be carried by one or more lever arms or other supportstructures. The relationship may alternatively be reversed between thedeployment catheter and the implant, such that one or more radiallyoutwardly extending projections on the implant engage a radiallyoutwardly extending recess on the interior wall of the deploymentcatheter. In general, a positive interference fit can be readilyaccomplished by a first locking surface on the catheter which isremovably engaged with a second, complementary locking structure on theimplant. Preferably, one of the first and second locking structures islaterally moveable to engage and disengage the implant, and a lock isprovided for releasably locking the first and second engagement surfacesto releasably retain the implant on the catheter.

FIG. 51 illustrates the proximal end of the balloon 400 attached to thedistal end of the catheter as described above.

FIG. 52 illustrate an embodiment of a stiffening wire 520 used tofacilitate the insertion of the catheter. The stiffening wire 520comprises an elongate flexible body, having a proximal end and a distalend. A handle 522 is provided at its proximal end. The length of thewire is sufficient to provide support to the catheter during insertion,and thus may be varied depending on the catheter dimensions which arediscussed elsewhere herein. Diameters are also based upon the ID of theinflation lumen of the intended catheter. In one embodiment, the wirecomprises an 0.050 inch OD wire or tube, which may be stainless steel orother material. A lubricious coating, such as PTFE may also be provided.To achieve more flexibility in distal region 524, the wire or tube maytaper throughout a tapered zone 528 to a smaller OD distally. A coilspring 526 may be carried concentrically around the tapered zone 528,and attached at a distal tip 530. This allows the guide wire to beincreasingly flexible distally.

The deployment and release of the inflatable orthopedic balloon 400 isnow described. A guide wire may be inserted into the injection lumen 432to stiffen the entire catheter to facilitate insertion of the balloon400. This guide wire may be inserted via the injection port 502. Ideallythis guide wire extends all the way to the distal end 402 of theballoon, and has a diameter that permits axial movement within the innerdiameter of the injection tube 430. The insertion of the balloon 400 maybe visualized by fluoroscopy of the distal marker 404 and the proximalmarker 418. The guide wire is removed prior to the injection of curablemedium into the balloon 400 via the injection lumen 432.

The injection port 502 is then connected to a pump, which pumps curablemedium into the balloon 400 through the injection tube 430. As theinjection tube 430 in the illustrated embodiment extends through theinner tubing 406 into or close to the distal end 402 of the balloon 400,the balloon is filled from the distal end 402 first. A vacuum isconnected to suction port 504. As described above, the suction tube 434extends through the valve assembly 420 of the balloon 400 to a pointjust distal of the proximal marker 418, and the inner tubing 406 of theballoon 400 is porous, This suction thus contributes to the filling ofthe balloon 400 with curable medium.

After the space 412 (as defined by the volume between the inner tubing406 and the outer wall 414 of the balloon 400) is filled with curablemedium, the luer lock 510 may be disengaged to allow the removal of theinjection tube 430 and the suction tube 434. Any space remaining in theinner tubing 406 is filled with curable medium as the injection tube 430is slowly pulled out. The valve assembly 420 of the balloon 400 preventsany curable medium from leaking.

A high frequency current is passed through the heating element 408 toaccelerate the curing of the curable medium in the balloon 400, as hasbeen discussed above in FIG. 47.

After the completion of the heating cycle, the catheter is removed fromthe balloon 400 by first sliding outer tube 450 proximally, exposing thelock tube 444. As described above, the lock tube 444 is slit. Withoutthe outer tube 450 around it, the rounded proximal surface of projection446 of the lock tube 444 will slide over and off the bottleneck 428 ofthe balloon 400 as the catheter handle 500 is pulled proximally. Thisaction will also disengage the inner electrical connector tube 438 fromthe inner electrical connector ring 422 and the outer electricalconnector tube 440 from the outer electrical connector ring 424. Theballoon 400 is thus left in place after the removal of the catheter.

Although the application of the present invention will be disclosed inconnection with connecting two adjacent vertebrae, the methods andstructures disclosed herein are intended for various other applicationssuch as to connect three or more vertebrae, as will be apparent to thoseof skill in the art in view of the disclosure herein. In addition, themethod may be used to stabilize the L5 vertebrae, using the cranial-wardportion of the sacrum as the vertebrae with which L5 is anchored.Furthermore, although the method is disclosed and depicted as applied onthe left side of the vertebral column, the method can also be applied onthe right side of the vertebral column, or both sides of the vertebralcolumn sequentially or simultaneously.

The method of the present invention involves percutaneously insertingone or more fusion devices into two or more than two adjacent vertebrae,either unilaterally or, preferably bilaterally, where a portion or allof at least one of the vertebrae is unstable, separated or displaced.The fusion devices reposition or fix the displaced vertebra or portionof the displaced vertebra to a position within the vertebral columnwhich is more stable or which causes less morbidity.

Referring now to FIG. 18 through FIG. 28, there are shown a series ofdrawings depicting various stages of the method of repositioning andfixing a displaced vertebra or portion of a displaced vertebra,unilaterally, according to the present invention. FIGS. 18-28 showpartial cutaway, perspective, midline sagittal views of a portion of avertebral column undergoing the method of the present invention.

The method will now be disclosed and depicted with reference to only twovertebrae, one which is either unstable, separated or displaced and oneof which is neither unstable, separated nor displaced. However, themethod can also be applied to three or more vertebrae simultaneously, aswill be understood by those with skill in the art with reference to thisdisclosure. Additionally, the method can be used to stabilize the L5vertebrae, using the cranial-ward portion of the sacrum as the“vertebrae” with which L5 is anchored. Further, though the method isdisclosed and depicted as applied on the left side of the vertebralcolumn, the method can also be applied on the right side of thevertebral column or, preferably, can be applied on both sides of thevertebral column, as will be understood by those with skill in the artwith reference to this disclosure.

First, the present method comprises identifying a patient who is asuitable candidate for undergoing the method. In connection with aspinal application, a suitable candidate has one or more unstablevertebrae, one or more portions of one or more vertebrae at least partlyseparated from the remainder of the vertebrae, one or more portions ofone or more vertebrae at least partly separated from the remainder ofthe vertebrae with potential or complete separation, or has one or morevertebrae or a portion of one or more vertebrae displaced from itsnormal position relative to the vertebral column, or has one or moreportions of one or more vertebrae at least partly separated from theremainder of the vertebrae and displaced from its normal positionrelative to the vertebral column. Further, the suitable candidate willnormally have either pain, loss of function or real or potentialinstability which is likely due to the separation or displacement, orseparation and displacement. If only a portion of the vertebra isunstable, separated or displaced, the portion of the vertebra that isunstable, separated or displaced will generally include at least part ofthe vertebral body and adjoining pedicle. However, other unstable,separated or displaced portions of a vertebra can be repositioned orfixed using the present method, as will be understood by those withskill in the art with reference to this disclosure. For example, asuitable patient can have a disease or condition such as spondylosis,spondylolisthesis, vertebral instability, spinal stenosis anddegenerated, herniated, or degenerated and herniated intervertebraldiscs, though actual indications require the expertise of one of skillin the art as will be understood by those with skill in the art withreference to this disclosure.

Next, the present method comprises making a stab incision in thepatient's skin overlying the patient's vertebral column at or near thelevel of the vertebrae or portion of vertebrae to be repositioned orfixed. In one embodiment, the incision is made at or near the level ofthe pedicle of the vertebra or portion of vertebra to be repositioned orfixed. The pedicle level is located preferably by identifying thepedicle shadow using fluoroscopy. In a preferred embodiment, the stabincision is made using a #11 scalpel blade.

Then, as shown in FIG. 18, an 11-gauge bone biopsy needle 202 or itsequivalent is placed through the stab incision to create a tract to theposterior periosteal surface of the vertebra 200 which is to bestabilized, repositioned or fixed. Next, the biopsy needle 202 is usedto make a small incision in the periosteum and into the cortex of thevertebrae.

Then, as shown in FIG. 19, a rigid, needle-tipped guidewire 204 having adiameter in the range of 0.035″ to about 0.060″ is inserted though thebiopsy needle 202 into the tract, through the periosteal incision andinto the cortex of the bone, and the guidewire 204 is advanced into theanterior aspect of the vertebral body 200 or into another suitableportion of the vertebrae 200, as will be understood by those with skillin the art with reference to this disclosure. Insertion of the guidewire204 is preferably accomplished using fluoroscopy. This process creates acontinuous tract from the skin surface into the anterior vertebral bodyor suitable portion of the vertebrae 200.

The biopsy needle 202 is then removed and the tract from the skinsurface to the nicked periosteal surface is enlarged by using ahigh-pressure fascial dilator balloon (not shown) over the needle-tippedguidewire. Then, the balloon is removed and a working sheath 206 isintroduced into the dilated tract. Alternately, a hard plastic ormetallic sheath with a central dilator is advanced over the guidewirefrom the skin surface to the periosteal surface. Next, a pilot hole maybe drilled using an over-the-wire drill bit driven by a hand held drill.

Next, as shown in FIG. 20, a bone screw 208 according to the presentinvention is introduced into the working sheath 206 over the guidewire204 by introducing the central lumen of the bone screw 208 over theproximal end of the guidewire 204. A screwdriver 210 according to thepresent invention is similarly introduced over the guidewire 204. Thebone screw 208 and distal portion of the screwdriver 210 are thenadvanced distally through the sheath 206 and the tract to the periostealsurface of the vertebral 200 until the proximal portion of the bonescrew 208 is engaged by the tip of the screwdriver 210. Torque isapplied to the bone screw 208 using the screwdriver 210 and the bonescrew 208 is advanced until the distal portion of the bone screw 208enters the anterior vertebral body or other suitable portion of thevertebra 200, while the portal of the bone screw 208 is exterior anddorsal to the vertebra 200 and the portal is open parallel to the longaxis of the vertebral column. Then, as shown in FIG. 21, the guidewire204, sheath 206 and screwdriver 210 are removed after satisfactoryplacement of the bone screw 208 has been obtained and confirmed byfluoroscopy. Additionally, bone matrix material such as a hydroxyapatitepreparation can be injected into the central lumen of the bone screw andthrough the one or more than one perforation, if present, to promotebone ingrowth.

The stages discussed above are repeated for at least one additionalvertebra 212 until each vertebra that is to be repositioned or fixed hasa bone screw 208 applied, and additionally for at least one vertebrawhich is neither unstable, separated nor displaced and which liesadjacent the cranial-most or caudal-most vertebra that is beingrepositioned or fixed. The bone screw 208 placed into the vertebra 212which is neither unstable, separated nor displaced is used as the anchorto reposition or fix each vertebra 200 which is unstable, separated ordisplaced as follows. As will be understood by those with skill in theart with reference to this disclosure, the bone screws can be placedinto the vertebrae in a different order to that described above.

After a bone screw is positioned in each vertebra, the portals areconnected using an inflatable connection rod according to the presentinvention where the rod is inserted between the portals of the bonescrews and inflated to create a rigid structure with the bone screws,thereby repositioning and fixing the one or more than one previouslyunstable, separated or displaced vertebra, or one or more previouslyunstable, separated or displaced portions of one or more vertebrae withthe vertebra that is neither unstable, separated nor displaced.Connection of the bone screws with the inflatable rod is accomplished asfollows.

Referring now to FIG. 22 and FIG. 23, a hollow needle 214, such as a 16gauge or 18 gauge needle, is inserted percutaneously andfluoroscopically advanced to the portal of one of the bone screws 208.While the hollow needle is shown engaging the bone screw 208 in thecranial-ward vertebrae 212, the hollow needle can engage the bone screw208 in the caudal-ward vertebrae 200 first, as will be understood bythose with skill in the art with reference to this disclosure. FIG. 23is a detailed view of FIG. 22.

Then, as shown in FIG. 24, a needle-tipped, semi-rigid guidewire 216 isintroduced through the lumen of the hollow needle 214 and into theportal of the bone screw 208 in the cranial-ward vertebrae 212. Thehollow needle 214 preferably has a Tuohy needle tip which causes theguidewire 216 to exit the hollow needle 214 perpendicular to thedistal-proximal axis of the bone screw 208 and parallel to the long axisof the vertebral column. Alternately, the hollow needle 214 can have anangled-tip modified Ross needle or other suitable structure as will beunderstood by those with skill in the art with reference to thisdisclosure.

In one embodiment, as further shown in FIG. 24, a guidewire directingdevice 218 according to the present invention is inserted percutaneouslybetween the portals of each bone screw 208 and the fork-tipped end isused to direct the advancing guidewire 216 through the second bone screwportal, and to reorient the guidewire 216 after the guidewire 216 haspassed through the portal on the bone screw 208 of the caudal-wardvertebrae 212.

In another embodiment, as further shown in FIG. 24, a guidewire capturedevice 219, such as a snare or grasping forceps, is insertedpercutaneously, caudal to the portal of the bone screw in thecaudal-ward vertebrae. The capture device 219 engages the guidewireafter it passes through the portal of the bone screw in the caudal-wardvertebra and allows the distal end of the guidewire to be pulled throughthe skin posteriorly to obtain control of both the proximal and distalends of the guidewire.

In another embodiment, the needle-tipped, semi-rigid guidewire 216comprises an outer helical, flat wire sheath and an inner retractablesharp tip stylet. Once the needle-tipped, semi-rigid guidewire isplaced, the stylet can be removed to allow for easier capture by thecapture device with less trauma to the surrounding tissue.

Then, as shown in FIG. 25, the entire guidewire tract is dilated using ahigh pressure balloon and a flexible introducer sheath 220 may be passedover the guidewire 216 along the entire guidewire tract exiting thecaudal-ward stab incision. The guidewire 216 is removed after theintroducer sheath 220 is placed. Alternatively, the implant is advancedover the wire 216 without the use of a sheath 220.

Next, as shown in FIG. 26, an uninflated, inflatable connection rod 222according to the present invention which is attached to a proximalpushing catheter 224 is advanced through the introducer sheath 220 untilthe inflatable connection rod 222 advances between the two portals andthe proximal end of the inflatable connection rod 222 lies cranial tothe portal on the bone screw 208 in the cranial-ward vertebra 212 whilethe distal end of the inflatable connection rod 222 lies caudal to theportal on the bone screw 208 in the caudal-ward vertebra 200. The sheath220 is removed and the placement is confirmed by fluoroscopy.

Then, as shown in FIG. 27, the balloon of the inflatable connection rod222 is inflated with a rapid setting, liquid polymer, or its equivalent,and the polymer is allowed to set fixing each bone screw 208 in relationto each other and repositioning and fixing the vertebra 200 or portionof the vertebra that was unstable, separated or displaced. In oneembodiment, the liquid polymer is or includes a two part epoxy or otherhardenable media such as those discussed elsewhere herein, and curing isaccelerated by the application of heat. The inflated balloon of theinflatable connection rod 222 expands radially beyond the diameter ofthe portals of each bone screw 208 which helps fix the bone screws 208in relation to each other.

Finally, as shown in FIG. 28, the delivery or pushing catheter 224 isdetached from the inflatable connection rod 222 by pulling on thepushing catheter 224 while resisting proximal movement of the inflatableconnection rod 222 to disengage the inflatable connection rod 222 fromthe pushing catheter 224 and the pushing catheter 224 is removed. Theinflatable connection rod 222 comprises a self-sealing valve whichprevents the polymer from leaking once the pushing catheter is detached.The vertebra is then fixed unilaterally. The method can be repeated onthe opposite side of the spinous processes of the patient's vertebraecolumn, thereby repositioning or fixing the one or more unstable,separated or displaced vertebrae or the one or more portions of one ormore vertebrae bilaterally. The access incisions are closed or sealed asnecessary and routine postoperative care administered.

Referring now to FIG. 29, there is shown a posterior perspective view ofa portion of a vertebral column which has had some vertebraerepositioned and fixed bilaterally according to the present invention.When bilateral fixation is accomplished, it is preferred to place allbone screws before connecting the portals with inflatable connectionrods.

In another embodiment of the present method, a directing sheath 180according to the present invention is advanced over a guidewire untilthe openings in the directing sheath 180 overlie the position in eachvertebra which will receive a bone screw 208. The bone screws 208 arethen placed as disclosed in this disclosure, but through the openings inthe directing sheath 180, which aligns the lumen in the directing sheathwith the portals of the bone screw 208. Then (not shown), a guidewire isinserted into the lumen of the directing sheath at the proximal end ofthe directing sheath and advanced until the guidewire passes througheach portal of the bone screws and exits the body through the lumen ofthe directing sheath at the distal end. The directing sheath is thenremoved by peeling the sheath apart along the scored lines and pullingthe two halves out from the body. The guidewire that was in the lumen ofthe directing sheath remains in place to guide the placement of theuninflated, inflatable connection rod. Alternately, the uninflated,connection rod can be inserted directly into the lumen of the directingsheath at the proximal end and advanced until the uninflated, inflatableconnection rod is properly positioned between the portals of the bonescrews. Referring now to FIG. 30 through 32, there are shown posteriorperspective views of a portion of a vertebral column undergoing themethod of the present invention using a directing sheath according tothe present invention, showing the bone screws placed through theopenings of the directing sheath. As can be seen in FIG. 30, thedirecting sheath 180 is positioned adjacent the vertebral column 196according to the present invention. Next as can be seen in FIG. 31,guidewires 198 are used to place bone screws 208 through openings 188 inthe directing sheath 180. Finally, as can be seem in FIG. 32, thedirecting sheath 180 is removed by the directing sheath 180 into twoseparate halves.

In one embodiment, there is provided a kit for performing methods of thepresent invention. The kit comprises a plurality of bone screwsaccording to the present invention. The kit can also comprise othercomponents of the system of the present invention, such as a guidewiredirecting device, an inflatable connection rod, the components of thepolymer system to be mixed and injected and a directing sheath. Inanother preferred embodiment, the kit also comprises a screwdriveraccording to the present invention. A control with electronic drivingcircuitry can also be provided, for thermal acceleration of thehardenable media.

Referring to FIG. 29, a first inflatable connection rod 222 a and asecond inflatable connection rod 222 b are illustrated as extendinggenerally in parallel with each other, and also generally in parallel tothe longitudinal axis of the spine. Deviations from this illustratedparallel relationship may also occur, in either or both of the lateralplane as well as the anterior/posterior plane. Such deviations fromparallel may be a consequence of anatomical variations, or proceduralchoices or irregularities as will be appreciated by those of skill inthe art. In any of these configurations, additional stability may beachieved by cross-linking the first inflatable connection rod 222 a withthe second inflatable connection rod 222 b. Thus, in accordance with afurther aspect of the present invention, there is provided a method andapparatus for cross-linking two or more inflatable connection rods.

Cross-linking may be accomplished in any of a variety of configurations,as will be apparent to those of skill in the art in view of thedisclosure herein. For example, a pair of laterally opposing pediclescrews 208 may be connected to each other by an inflatable crossbar orsolid crossbar as will be apparent from the disclosure herein.Alternatively, the body of the two opposing inflatable connection rods222 a and 222 b can also be connected by a crossbar. Although thepresent discussion will focus primarily upon the latter construction, itis to be understood that the present invention contemplates any crossconnection between a left and right connection rod, preferably through aprocedure in which each of the connection rods or crossbars is installedin a less invasive or minimally invasive procedure.

Referring to FIG. 33, a side elevational view of a portion of the spineis illustrated. A first and second pedicle screws 208 have beenpositioned in accordance with procedures discussed previously herein. Ahollow needle 214 is illustrated, for guiding a “rocketwire” orguidewire 216 through the coaxial apertures in the first and secondpedicle screws 208.

FIG. 33 additionally illustrates a cross tie deployment system 230,partway through a deployment procedure. The cross tie deployment system230 comprises an access sheath 232. Access sheath 232 comprises anelongate tubular body having a proximal end and a distal end, and acentral lumen extending therethrough. In general, the central lumen willhave a diameter within the range of from about 24 French to about 30French, although other diameters may be utilized depending upon the sizeof the device to be deployed. The access sheath 232 is positionedthrough tissue along an axis which intersects the path of the guidewire216, as is advanced from a first pedicle screw 208 through an aperturein a second pedicle screw 208, as illustrated.

A cross tie support 248 is axially movably positioned within the accesssheath 232. Cross tie support 248 is connected at a distal end 249through a releasable connector 246 to a cross tie 234. Cross tie 234facilitates connection of a crossbar with a primary inflatableconnection rod, to achieve cross linking of the orthopedic fixationsystem.

Although a variety of structures for cross tie 234 can be utilized, oneconvenient construction is illustrated in FIG. 37. In general, the crosstie 234 includes a first connector 236 such as a first aperture 238 forreceiving an inflatable connection rod 222 as has been discussedpreviously herein. In one implementation, the aperture 238 has an insidediameter of approximately 6 mm. However, diameters of the first aperture238 may be varied widely, depending upon the diameter of the inflatableconnection rod 222, and the desired physical performancecharacteristics.

The cross tie 234 additionally comprises a second connector 240, such asa second aperture 242. The second aperture 242 is adapted to receive acrossbar 222 c, as illustrated in FIGS. 35 and 36. In the illustratedcross tie 234, a longitudinal axis extending through the first aperture238 is generally perpendicular to a longitudinal axis extending througha second aperture 242, and offset by a spacing distance which willdetermine the anterior-posterior spacing between the axis of aninflatable connection rod 222 a and a corresponding crossbar 222 c. Inone embodiment, the overall as mounted anterior-posterior length of thecross tie 234 is approximately 16 mm, and the width of the cross tie 234is no more than about 8 mm.

The cross tie 234 is held in place during the procedure by a cross tiesupport 248 through a releasable connector 246. The releasable connector246 facilitates the positioning of the cross tie 234 during thedeployment step, but enables decoupling following proper positioning ofat least an inflatable connection rod 222 a and possibly also thecrossbar 222 c. Any of a variety of releasable connection structures maybe utilized, such as a threaded distal end on the cross tie support 248,which threadably engages an aperture on the cross tie 234.

As illustrated in FIGS. 33, 36 and 37, the cross tie 234 is held inposition by the cross tie support 248 such that the longitudinal axisextending through the first aperture 238 is collinear with the path ofthe guidewire 216. The longitudinal axis of the second aperture 242extends transversely such that it aligns with a second aperture 242 in asecond cross tie 234 to accomplish the cross-linked constructionillustrated in FIGS. 35 and 36.

Referring to FIG. 34, the first inflatable connection rod 222 a isillustrated as inflated after having been positioned through the firstaperture 238 on the cross tie 234, as well as through the approximatelycollinear apertures on a pair of bone screws 208. This is accomplishedby advancing the guidewire 216 through the first bone screw, then thefirst aperture 238 and then the second bone screw 208, as illustrated inprogress in FIG. 33. The connection rod 222 a may then be advanced overthe wire and inflated following the inflatable connection rodimplantation procedures discussed previously herein.

Preferably, the first aperture 238 is dimensioned with respect to theconnection rod 222 a such that a secure fit is provided between theinflatable connection rod 222 a and cross tie 234 following completecuring of the curable media. If shrinkage of the curable media iscontemplated, the first aperture 238 may be defined within an annularring on the frame 244 which has an expansion break extendingtherethrough. In this manner, inflation of the inflatable connection rod222 a can be accomplished such that the expansion break allows a slightenlargement of the diameter of the first aperture 238. Upon transverseshrinkage of the inflatable connection rod 222 a during the curingprocess, the natural bias imparted by the frame 244 allows the firstaperture 238 to shrink, thereby retaining a tight fit with theinflatable connection rod 222 a throughout a range of diameters. Thisconstruction may also be applied to the apertures extending through thebone screws 208, as well as the second apertures 242.

The cross tie support 248 is illustrated in FIG. 34 as detached from thecross tie 234, such as by unscrewing the releasable connector 246. Thismay be accomplished before or after positioning of the crossbar 222 c,depending upon the clinical judgment of the practitioner.

The final construction is illustrated in FIG. 35. As seen therein, acrossbar 222 c extends between a first cross tie 234 carried by thefirst inflatable connection rod 222 a and a second cross tie 234 carriedby the second inflatable connection rod 222 b. The crossbar 222 c may bepositioned through the pair of opposing apertures 242 using the sametechniques discussed and illustrated previously herein for theimplantation of the inflatable connection rods 222. The initial positionof a curved needle and guidewire for positioning the crossbar 222 c isschematically illustrated in FIG. 36.

Although only a single crossbar 222 c is illustrated, two or three orfour or more crossbars 222 c may alternatively be used, depending uponthe axial lengths of the inflatable connection rods 222 a and 222 b, andthe desired structural integrity of the finished assembly. In addition,although the crossbar 222 c is illustrated as extending generallyperpendicular to the longitudinal axis of each of the inflatableconnection rods 222 a and 222 b, the crossbar 222 c may cross each ofthe inflatable connection rods 222 at any of a variety of angles rangingfrom approximately +45° to −45° with respect to the illustratedposition. Thus, the crossbar 222 c may be implanted at a diagonal if thedesired structural integrity can be thus achieved.

The crossbar 222 c may comprise any of a variety of forms. For example,the crossbar illustrated in FIG. 35 may be identical in construction toany of the inflatable connection rods discussed previously herein.

In an alternate application of the cross-linking technology of thepresent invention, the crossbar is constructed in a manner which enableselimination of the separate cross tie 234. Referring to FIGS. 40-43, thecrossbar comprises a first portal 250, for receiving a first inflatableconnection rod 222 a, and a second portal 252 for receiving a secondinflatable connection rod 222 b. First portal 250 and second portal 252are spaced apart by an elongate tubular body 254. Body 254 may be asolid element, such as a polymeric extrusion, molded part or metal rod.Alternatively, body 254 comprises a tubular sleeve, such as illustratedin FIGS. 40-42. In the illustrated embodiment, the tubular sleeve isprovided with a plurality of circumferentially extending slots 254, topermit flexibility of the crossbar 222 c during deployment. Slots 254may be formed such as by laser cutting a stainless steel,nickel-titanium alloy or other tube.

FIG. 41 schematically illustrates the distal end of a deployment system258 for deploying the crossbar 222 c of FIG. 40. The tubular body 254 iscarried by a dilator 260 which extends axially therethrough. In oneapplication, the dilator 260 is approximately 21 French, foraccommodating a tubular body 254 having an inside diameter of about 7 mmand an outside diameter of about 8 mm.

The 21 French dilator 260 is advanced over a stiff 0.038″ guidewire,with an 8 French catheter. A 24 French pusher sheath 262 is positionedproximally of the tubular body 254.

Using this deployment system, the tubular body 254 may be positionedrelative to two pairs of bone screws 208 as illustrated schematically inFIG. 42. A first pair of bone screws 208 a and 208 b contain apertureswhich coaxially align with the first portal 250. A second pair of bonescrews 208 c and 208 d carry apertures which are coaxially aligned witha second portal 252. Once positioned as illustrated in FIG. 242, aguiding assembly such as a curved needle 214 and a rocket wire 216 maybe advanced as illustrated in FIG. 42. An inflatable connection rod 222a may thereafter be advanced along the wire, and inflated to secure thefirst and second bone screws 208 a and 208 b, and also the crossbar 222c. A similar procedure may be accomplished to install a secondinflatable connection rod 222 b.

The tubular body 254 may by itself provide sufficient cross-linkingstrength for the intended purpose. Alternatively, the tubular body 254may be filled with a curable media 266 to enhance the structuralintegrity of the resulting assembly. For example, as illustrated in FIG.43, the deployment system 258 may additionally comprise an inflatablecontainer such as an inflatable connection rod previously disclosedherein, in communication with a source of curable media through aninflation lumen. Depending upon the construction of the inflatablecontainer, it may be filled with a hardenable media 266 either prior toor following positioning of the first inflatable connection rod 222 aand second inflatable rod 222 b as discussed previously herein.

The embodiment of FIGS. 40-43 is illustrated in position within thepatient, in FIGS. 38 and 39. As can be seen from FIGS. 38 and 39, thecrossbar 222 c resides within the plane that extends through theapertures in the bone screws 208. Thus, the crossbar 222 c in theconfiguration illustrated in FIGS. 38 and 39 is lower profile, orpositioned anteriorly of the crossbar 222 c in the embodiment of FIGS.34 and 35. The location of the crossbar 222 c in FIGS. 38 and 39 is not,however, precisely to scale or in the exact or only implantable locationin the spine. For example, the crossbar 222 c may extend laterallythrough a space in-between an adjacent pair of caudal and cephaladspinous processes. If the crossbar 222 c is preferably positioned at amore caudal or cephalad position than the opening between adjacentspinous processes, or if the crossbar 222 c is preferably positionedfarther anteriorly than would be permitted by the transverse process orother bony structure, the crossbar 222 c may extend through an aperturebored through the bone, or portions of the bone may be removed. Any of avariety of bores or drills may be utilized to bore a transverseaperture, such as through a spinous process. The crossbar 222 c maythereafter be advanced through the bore and locked into place using thefirst and second support structure 222 a and 222 b as is disclosedelsewhere herein.

Although the present invention has been described in terms of certainpreferred embodiments, other embodiments of the invention includingvariations in dimensions, configuration and materials will be apparentto those of skill in the art in view of the disclosure herein. Inaddition, all features discussed in connection with any one embodimentherein can be readily adapted for use in other embodiments herein. Theuse of different terms or reference numerals for similar features indifferent embodiments does not imply differences other than those whichmay be expressly set forth. Accordingly, the present invention isintended to be described solely by reference to the appended claims, andnot limited to the preferred embodiments disclosed herein.

1-28. (canceled)
 29. A method of stabilizing an orthopedic fracture,comprising: inserting at least two anchors having portals into a bone;delivering an orthopedic device comprising an inflatable balloon to thebone; inflating said balloon with a stiffening material; and heating themedia above body temperature to accelerate stiffening of the stiffeningmaterial; wherein said orthopedic device extends through said portals,such that said inflating fixes said anchors in relation to one another.30-40. (canceled)
 41. A method of forming an orthopedic device at atreatment site within the body of a patient, comprising the steps of:positioning an outer wall at the treatment site within the patient, theouter wall defining a chamber therein; introducing a hardenable mediainto the chamber; and heating the hardenable media to acceleratehardening, to form the orthopedic device.
 42. A method of forming anorthopedic device as in claim 41, wherein the positioning step comprisespositioning the outer wall between two bone anchors.
 43. A method oftreating a patient, comprising the steps of: securing a first rod at afirst site in the patient; securing a second rod at a second site in thepatient; introducing a curable media in between the first and secondrods to form a cross link; and heating at least a portion of the mediato a temperature of at least about 50 degrees C., to accelerate curingof the media thereby linking the first rod to the second rod.
 44. Amethod of treating a patient as in claim 43, wherein the introducingstep comprises introducing the curable media into a tubular mediasupport structure extending between the first and second rods.
 45. Amethod of treating a patient as in claim 44, wherein the supportstructure comprises a balloon.
 46. A method of treating a patient as inclaim 43, wherein the method is accomplished percutaneously.
 47. Amethod as in claim 43, wherein the linking step comprises positioning aballoon between the first and second rods and introducing the media intothe balloon. 48-66. (canceled)
 67. A method of stabilizing an orthopedicfracture, comprising: inserting at least two anchors having portals intoa bone; delivering an orthopedic device comprising an inflatable balloonthrough the portals; inflating said balloon with a hardenable material;and elevating the temperature of at least a portion of the hardenablematerial to above about 45° C.; wherein the inflating step fixes saidanchors in relation to one another.